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Re: [Libguestfs] [PATCH] Don't assume grub is on a separate boot filesystem



On Thu, Aug 13, 2009 at 12:21:16PM +0100, Matthew Booth wrote:
> Paths in grub.conf are relative to the filesystem containing it. grub parsing
> currently assumes that it is on /boot, and will fail if it isn't, for example
> because a guest only has a single partition.
> 
> This patch makes grub parsing work harder to work out what grub paths are
> relative to. Firstly, it looks for a previous detected 'linux-grub' filesystem.
> If this isn't found, it tries to work out which filesystem contains
> /boot/grub/menu.lst and uses that.
> ---
>  perl/lib/Sys/Guestfs/Lib.pm |   56 +++++++++++++++++++++++++++++++++++++++++-
>  1 files changed, 54 insertions(+), 2 deletions(-)
> 
> diff --git a/perl/lib/Sys/Guestfs/Lib.pm b/perl/lib/Sys/Guestfs/Lib.pm
> index 72b0f7d..89f2aa6 100644
> --- a/perl/lib/Sys/Guestfs/Lib.pm
> +++ b/perl/lib/Sys/Guestfs/Lib.pm
> @@ -1435,6 +1435,56 @@ sub _check_for_applications
>      $os->{apps} = \ apps;
>  }
>  
> +# Find the path which needs to be prepended to paths in grub.conf to make them
> +# absolute
> +sub _find_grub_prefix
> +{
> +    my ($g, $os) = @_;
> +
> +    my $fses = $os->{filesystems};
> +    die("filesystems undefined") unless(defined($fses));
> +
> +    # Look for the filesystem which contains grub
> +    my $grubdev;
> +    foreach my $dev (keys(%$fses)) {
> +        my $fsinfo = $fses->{$dev};
> +        if(exists($fsinfo->{content}) && $fsinfo->{content} eq "linux-grub") {
> +            $grubdev = $dev;
> +            last;
> +        }
> +    }
> +
> +    my $mounts = $os->{mounts};
> +    die("mounts undefined") unless(defined($mounts));
> +
> +    # Find where the filesystem is mounted
> +    if(defined($grubdev)) {
> +        foreach my $mount (keys(%$mounts)) {
> +            if($mounts->{$mount} eq $grubdev) {
> +                return "" if($mount eq '/');
> +                return $mount;
> +            }
> +        }
> +
> +        die("$grubdev defined in filesystems, but not in mounts");
> +    }
> +
> +    # If we didn't find it, look for /boot/grub/menu.lst, then try to work out
> +    # what filesystem it's on. We use menu.lst rather than grub.conf because
> +    # debian only uses menu.lst, and anaconda creates a symlink for it.
> +    die(__"Can't find grub on guest") unless($g->exists('/boot/grub/menu.lst'));
> +
> +    # Look for the most specific mount point in mounts
> +    foreach my $path qw(/boot/grub /boot /) {
> +        if(exists($mounts->{$path})) {
> +            return "" if($path eq '/');
> +            return $path;
> +        }
> +    }
> +
> +    die("Couldn't determine which filesystem holds /boot/grub/menu.lst");
> +}
> +
>  sub _check_for_kernels
>  {
>      my ($g, $os) = @_;
> @@ -1443,6 +1493,8 @@ sub _check_for_kernels
>          # Iterate over entries in grub.conf, populating $os->{boot}
>          # For every kernel we find, inspect it and add to $os->{kernels}
>  
> +        my $grub = _find_grub_prefix($g, $os);
> +
>          my @boot_configs;
>  
>          # We want
> @@ -1474,7 +1526,7 @@ sub _check_for_kernels
>  
>              # Check we've got a kernel entry
>              if(defined($grub_kernel)) {
> -                my $path = "/boot$grub_kernel";
> +                my $path = "$grub$grub_kernel";
>  
>                  # Reconstruct the kernel command line
>                  my @args = ();
> @@ -1508,7 +1560,7 @@ sub _check_for_kernels
>  
>                      unless($@) {
>                          $config{initrd} =
> -                            _inspect_initrd($g, $os, "/boot$initrd",
> +                            _inspect_initrd($g, $os, "$grub$initrd",
>                                              $kernel->{version});
>                      } else {
>                          warn __x("Grub entry {title} does not specify an ".
> -- 
> 1.6.2.5
> 
> _______________________________________________
> Libguestfs mailing list
> Libguestfs redhat com
> https://www.redhat.com/mailman/listinfo/libguestfs

Can't see any problem with that, ACK.

Rich.

-- 
Richard Jones, Emerging Technologies, Red Hat  http://et.redhat.com/~rjones
virt-df lists disk usage of guests without needing to install any
software inside the virtual machine.  Supports Linux and Windows.
http://et.redhat.com/~rjones/virt-df/


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